The present disclosure relates to analog circuits and in particular to analog to digital conversion circuitry.
Unless otherwise indicated herein, the approaches described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
A software-defined radio (SDR) system is a radio communication system where components that have been typically implemented in hardware (e.g., mixers, filters, amplifiers, modulators/demodulators, detectors, etc.) are reconfigurable by means of software. A basic SDR system typically comprises an antenna connected to a radio frequency (RF) front-end. An output of the RF front-end may then feed into a computing device (e.g., personal computer, mobile device, etc.).
Receiver front-ends typically use a variable-frequency oscillator and mixer to tune the desired signal to a common intermediate frequency or baseband, where it is processed by an analog filter and sampled by an analog-to-digital converter (ADC). Typical ADC's lack the dynamic range to pick up low-power radio signals. Accordingly, a low-noise amplifier (LNA) is typically provided upstream of the ADC and before the mixer. If spurious signals are present at the antenna (which is typical), these compete with the desired signals. They may introduce distortion in the desired signals, or may block them completely. A common solution is to put a band-pass filter between the antenna and the amplifier. The path for SDR designs involves the reduction of the base-band analog section of the wireless receiver in favor of a more flexible digital one.